The onaxis magnetic field strength 15cm from a small bar mag

The on-axis magnetic field strength 15cm from a small bar magnet is 5.5T.

Part A

What is the bar magnet\'s magnetic dipole moment?

Part B

What is the on-axis field strength 21cm from the magnet?

Solution

A ) Magnetic field, B = (u0 2M ) / (4 pi r^3)

where M = magnetic moment

5.5 x 10^-6 = (4pi x 10^-7 x 2 x M) / (4 pi 0.15^3 )

M = 0.0928

B) r = 0.21 cm

B = (4pi x 10^-7 x 2 x 0.0928 ) / (4 pi 0.21^3 )

B = 2 x 10^-6 T Or 2 uT